Retrospection, n.
The act, or the faculty, of looking back on things past.
Shades of meaning
Fernald has no entry of its own for retrospection; he lists it under memory.
Where he writes about it:
Reminiscence is a half-dreamy memory of scenes or events long past; retrospection is a distinct turning of the mind back upon the past, bringing long periods under survey. — from memory
Retrospection is to reminiscence much what recollection is to remembrance. — from memory